Carburetor throttle body vent



Sept. 28, 1954 wELDY 2,690,331

CARBURETOR THROTTLE BODY VENT Filed Oct. 18, 1951 IN VEN TOR.

A TTQRNEYS Patented Sept. 28, 1954 CARBURETOR THROTTLE BODY VENT Morton E. Weldy, Holly, Mich., assignor to General Motors Corporation, Detroit, Mich., a. corporation of Delaware Application October 18, 1951, Serial No. 251,878

5 Claims. 1

This invention relates to charge forming devices for engines and has particular relation to a charge forming device having means for conducting explosive fluid from the induction passage leading to the charge forming device after the operation of the engine is discontinued.

In charge forming devices as now constructed it is possible to form an explosive charge in the induction passage leading to the engine after the operation or the engine is discontinued. Such an explosive charge may be formed more readily as a result of the use of the exceptionally high volatile fuels that are supplied to facilitate the starting of engines during cold weather. When these high volatile fuels are employed there is a tendency for the fuel to percolate in. the carburetor jet or jets, this percolation being due to the formation of vapor in the carburetor float chamber and the passages leading therefrom to the induction passage. This vaporous fuel is not only capable of forming an explosive charge when it is released in the induction passage of an engine, but the movement thereof through the carburetor jets tends to form a vapor lift pump which tends to pump unvaporized fuel into the induction passage along with the vaporized fuel.

Such percolating or pumping may continue for as much as twenty or thirty minutes after the engine is stopped. Since the carburetor throttle is closed at this time, the vaporous fuel discharged from the carburetor jet or jets will mix with the air to form what may become an explosive charge in the induction passage of the engine anterior to the throttle. The liquid fuel so discharged will spread out over the various relatively warm surfaces of the jets and other parts of the carburetor and this liquid also will become vaporized by the transfer of heat from other relatively warmer parts of the engine. The charge so formed will tend to diffuse outwardly in the induction passage of the engine and may move far enough away from the throttle valve to reach various enlarged compartments formed. in the induction passage such as the resonating and other chambers formed in cleaners and silencers with which the induction system may be provided. The charge, when so diffused into these various compartments, may become pocketed therein to such an extent that a large part of the explosive charge will remain in these pockets in the event the engine is started within a predetermined time after being stopped. If a backfire in the inlet manifold occurs upon starting the engine, the flame of this backfire will proceed outwardly through the induction passages of the engine and may ignite the explosive charge previously formed in the carburetor and diifused outwardly into the various pockets referred to. Under such circumstances the flame from the backfire may ignite these explosive charges in one or more of these pockets and tend to cause either fire or an explosion that may result in damage or destruction of the cleaner or silencer or other parts of the charge forming device or the engine.

It has been customary heretofore to provide flame arresting devices across various pockets in which explosive charges might collect when the engine is not in operation. The theory of such flame arresters is that they will quench the flame resulting from a backfire and prevent it from igniting the explosive charge contained in such pockets.

It is now proposed to remove any such explosive charge that might be formed from the induction system of the engine after the engine has been stopped and before the explosive charge has an opportunity to diffuse outwardly in the induction system and to collect in any pockets where it might be exploded by a backfire that might occur when the engine is started. To accomplish such purpose it is proposed to provide an opening or other suitable means associated with the induction passage of the engine so that the charge that may be formed in the induction passage and after the engine is stopped may be moved inwardly rather than outwardly within the induction passage of the engine and may be removed from the induction passage at a position adjacent the throttle valve of the engine. When such means is provided the charge that might otherwise be formed by this percolating and pumping from the carburetor jets will be removed from the induction system as it is formed. With such construction no opportunity will be presented for the charge to become pocketed and to explode if a backfire occurs upon starting the engine.

Figure 1 illustrates a fragmentary view of an internal combustion engine having an induction system embracing the principles of the invention. Figure 1 illustrates the fragmentary structure partly in elevation and partly in longitudinal section.

Figure 2 is a cross sectional view of a part of the structure taken substantially in the plane of line 22 on Figure 1.

In Figure 1 there is indicated generally at it a piston and cylinder type internal combustion engine having an induction system or charge forming device indicated generally at H. The

induction system or charge forming device II comprises an inlet manifold 12, a carburetor 13, an intake silencer l4 and an air cleaner IS. The charge forming device H is adapted to form an explosive charge consisting of hydrocarbon fuel and air, and to supply such charge to the cylinders of the engine through an induction passage IT. The induction passage l1 extends through the air cleaner 18, the silencer M, the carburetor l3 and the inlet manifold 12.

It will be apparent that the induction 9 stem H may include any number of devices to be employed in processing the explosive charge delivered to the engine by the inlet manifold 12. For example, the induction system H may include elements in addition to the cleaner and silencer Hi and M respectively, or it may not include either or both of the latter two elements. In any event, it is intended that the term induction passage shall include a passage through all of the elements which are employed in addition to the carburetor E3 in forming and processing the explosive charge to be delivered to the engine by the inlet manifold i2.

As illustrated in Figure 1, it will be apparent that the induction passage originates in an annular air inlet [8 through which air is supplied to the air cleaner l5. The inlet H3 extends downwardly into the oil sump it of the cleaner from. which it is directed upwardly into the cleaner filtering element 2! by an annular baiile indicated at 22. The upper part of the cleaner is formed in such a way as to provide a dome or plenum chamber 23 and into which the cleaned and filtered air is discharged from the filter element 2!. Projecting into the central part of the dome or plenum chamber 23 is the inlet end of a tube or conduit 24 through which the air is conducted into and partly through the silencer I4. Within the silencer 54 the tube 24 terminates Within a silencer outlet tube or conduit indicated at 25. The annular space 22 between the tubes 24 and 26 provides an inlet to a tuned resonating chamber or compartment 29 with which the silencer i4 is provided. The silencer I4 has a second resonating chamber or compartment indicated at 3i which communicates with chamber 29 through tube 32. The end of the silencer I4 beyond the tube 26 is formed in such a way as to provide a silencer outlet 33 which is connected by an angularly disposed coupling member 34 to the inlet 36 of the carburetor [3. As is shown by Figure 2, th carburetor l3 has two induction passages extending therethrough from the single inlet passage indicated at 38. These induction passages are indicated by the numerals 31 and provide a continuation of the induction passage :1 to the cylinders of the engine l0. Each of the induction passages is provided with a throttle valve 38 secured to a single throttle valve actuating shaft 39 projecting diametrically across the induction passages indicated at 31. Above the throttles 38 each of the induction passages 31 is formed in such a way as to provide outer V enturi tubes 4i having inner concentric Venturi tubes 43 disposed therein and projecting upwardly within the carburetor inlet 36. Upwardly disposed carburetor jets 44 project within and terminate adjacent the axes of the inner Venturi tubes indicated at 43. The jets 44 are supplied with liquid fuel from the carburetor float chamber by upwardly directed fuel supply passages indicated at 46. The flow of air to the jets 44 and the induction passages 31 is controlled by a single choke valve 45 which projects across the inlet passage 36 above the inlet to the passages 31.

Figures 1 and 2 may be said to illustrate closed positions of the throttle valves 38. This is the position occupied by each of the throttle valves after the operation of the engine has been discontinued. In such closed positions it will be noted that the throttle valves 38 are disposed angularly across the passages 31 in such manner that one edge of each throttle valve is somewhat lower than the other in transverse relation to the axis of the shaft 39. Immediately above the lower edge of each throttle valve 38 is formed a small opening 41 extending across the walls of the inlet or induction passages 31. These openings 41 provide open communication between the induction passages 31 and the atmosphere. While it is desirable to have these openings provide open communication between the interior of the passages 31 and the atmosphere after the engine is stopped, it is not necessary to have these sages remain open during the operation of the engine. Valves which will close the passages through the openings 41 whenever the pressure of the atmosphere exceeds the pressure Within the induction passages 31 may be provided if such valves are considered desirable. However, it is not necessary to employ such valves because it is easily possible to adjust the carburetor so that it will operate perfectly with a small amount of air that the passages 41 will admit to the induction passages 31 during the operation of the engine. It is preferable, however, to maize the openings 41 relatively small. It has been found that drilled openings of about of an inch in diameter are large enough to perform the function for which these openings are provided.

It will be understood that the throttles 38 and the induction passages 31 may be provided with suitable by-pass and control means which will permit the engine to be started and operated at idling speed with the throttles 38 in the pos on shown and usually referred to as the closer throttle position.

It will be apparent that the engine may be started and may be operated at any desired speed with the charge forming device ll oper-- ating in the usual manner. However, when the engine is stopped the openings 41 will drain from the induction passages 31 any explosive mixture which may be formed as a result oi percolation or pumping of liquid fuel from the jets 44. This draining by gravity of the explosive mixture from the region surrounding the jets 44 will prevent the explosive mixture from difiusing upwardly within the induction passage 11 and from filling or partly filling the various pockets and compartments in the silencer l4 and the cleaner l3 such as the resonating chambers 29 and 32, the dome 23, the space beyond the bafile 22 within the oil sump I9 and the space below the inlet end of the conduit 24 and within the filter element 2!. If the engine backfires in the inlet manifold I? after being started, the flame resulting from the backfire will merely progress outwardly through the induction passage 11 by the shortest route between the manifold l2 and the inlet it to the cleaner I6. The various pockets in the cleaner and silencer therefore will not be afiected by the backfire as might be the case if these pockets had been filled with explosive charges.

I claim:

1. A charge forming device comprising a body having a downdraft passage therein adapted to conduct an explosive charge to the cylinders of an internal combustion engine, a throttle valve in said passage adapted normally to remain in closed position when the engine is not in operation and vent means formed in said body adjacent and anterior to the closed position of said throttle for exhausting by gravity any explosive charge contained in said passage above said throttle after the operation of said engine is discontinued.

2. A charge forming device for internal combustion engines comprising a body having a downdraft passage formed therein and adapted to conduct an explosive charge to said engine for operating said engine, a throttle valve in said passage for controlling the flow of said mixture to said engine, means in said passage above said throttle for supplying fuel to said passage for forming said explosive charge, and a vent between said means and said throttle for exhausting any explosive charge from said passage above said vent by gravity flow of fluid through said vent and after the operation of said engine is discontinued and said throttle is substantially closed.

3. A charge forming device for internal combustion engines comprising a body having a downdraft passage therein for conducting an explosive charge to the cylinders of an engine, a valve in said passage for controlling the flow of said charge to said cylinders, a silencer having a resonating chamber formed therein and connected to the upper end of said passage, said silencer being formed to provide a conduit extending therethrough for the flow of air through said silencer to said upper end of said passage and a connecting passage between said conduit and a lower part of said resonating chamber where an explosive charge formed in said carburetor above said throttle may flow by gravity and collect when said engine is not running and said throttle is substantially closed, means between said valve and said resonating chamber for supplying fuel to said passage for forming said explosive charge, and means for exhausting said passage between said throttle and said resonating chamber for removing from said passage any explosive charge contained in said passage after the operation of said engine is discontinued.

4. A charge forming device for internal combustion engines comprising a body having an induction passage therein for supplying an explosive charge to the cylinders of an engine, a throttle valve for controlling the flow of said charge through said passage, means for supplying fuel to said passage for forming said charge, and means between said throttle valve and said fuel supplying means for exhausting any explosive charge formed in said passage after the operation of said engine is discontinued.

5. A charge forming device for engines comprising a body having an induction passage formed therein for conducting an explosive charge to an engine, a throttle valve in said passage for controlling the flow of said charge to said engine, and vent means formed in said body anterior to said throttle and positioned to drain by gravity and toward said throttle any explosive charge contained in said passage anterior to said throttle after the operation of said engine is discontinued.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,722,462 Gage July 30, 1929 2,322,895 Steensen June 29, 1943 2,479,614 Gove Aug. 23, 1949 

